This invention relates to a controlled process for improving the yields of heavier olefins by using a substantially narrow range of lighter olefin-containing hydrocarbon feed stock which are fed into a reaction distillation column at a predetermined point and using varying arrangements of isomerizing and disproportionating catalysts in relation to the point of feeding the narrow range of lighter olefin-containing hydrocarbon feed stock. The controlled process provides for keeping the reaction mixture in a state of vapor/liquid phase equilibrium for separating the lighter products overhead and collecting the heavier reaction products in the bottoms by maintaining controlled pressure and temperature profiles in relation to the narrow range of lighter olefin-containing hydrocarbon feed stock being used and the desired range of heavier olefin-containing hydrocarbon products desired as product in the bottoms of the reaction distillation column. Further at least one or more zones for the purpose of vapor/liquid contacting are created in the reaction distillation column for improving the separation of lighter reaction olefin products from the heavier reaction olefin products and the olefin-containing hydrocarbon feed stock and for reducing the cost of the process.
It is well known in the prior art to use metal catalysts to react/split and recombine (disproportionate) hydrocarbon molecules, which contain olefinic or double bonds between the carbon atoms. This reaction of splitting and recombining the hydrocarbon molecules at the double bonds creates olefin hydrocarbon molecules of varying size depending on the feed stock make up and where the double bonds occurred on the feed stock molecules, but it does not necessarily give an end product with a high commercial value.
For example some of the earlier prior art reacted propylene to make ethylene and butene, or conversely make propylene from ethylene and butene in the presence of metal catalysts, which gave an olefin product but the product was not greatly different in value from the reactants. However, as these reactions are reversible, they will proceed, at most, to equilibrium, which limits the yield of the desired products. The prior art generally described only liquid phase reactions with heterogeneous catalyst in fixed beds, fluidized beds or moving beds for generally controlling approach to equilibrium of olefin-containing reactant and product mixtures.
The prior art also attempted to use other process variables like longer residence time in such systems and higher temperatures to achieve better approach to equilibrium and to shift equilibrium to a more favorable to desired products in disproportionating reactions, but they generally led to increased isomerization and other by-product reactions which were undesirable in the desired product.
Some of the prior art taught improved selectivity and conversion of reactions using 1- and 2-butene to ethylene, propylene, 2-pentene and 3-hexene by using a reactive distillation column, in the presence of a rhenium oxide as a disproportionation catalyst. In this prior art the catalysts served as a distillation substrate to facilitate a phase transfer of some of the lighter products out of the liquid phase. In this particular system the conversion and yields went up but the reaction proceeded to ethylene and propylene as the light ends and only to 2-pentene, 3-hexene as the heavy ends, which were of not much more value than the beginning feed stock used to generate them.
The prior art is replete with teaching of methods and processes for improving yields of medium-range olefins by reacting high carbon number molecule olefins with a low carbon number molecule olefins by simultaneous disproportionating and isomerizing of these olefins. In this process both the high carbon number molecule olefins and low carbon number molecule olefins are kept in a single liquid phase and the reaction process is allowed to reach near equilibrium for the formation of midrange olefins, which are detergent-range linear internal (C10-C16) olefin from a feedstock of light (C4-C9) and heavy (C16-C20+) alpha-olefins. Some variations of these prior art patents are even used to produce commercial linear alcohols.
These prior art patents utilized the isomerization process, which distributed the location of the double bond in the olefin molecules to make possible the production of a wider range of olefins, which readily worked if one was attempting to generate a mid-range detergent grade olefin from light and heavy alpha and internal olefins. In these been used to facilitate the isomerization of the double bonds between the carbon molecules and to create a wider range of internal olefins to be reacted to form the mid-range olefins.
Further the prior art has disclosed many processes using both an isomerization and disproportionation catalysts in a single liquid phase, elevated temperatures, and elevated pressure to attempt to achieve a desired range of products for a broad base of olefin-containing hydrocarbon feed stock, with only limited success due to limitation of equilibrium and a large range of olefin-containing hydrocarbons mixed together, which required further processing to separate the narrow desired range from both the lighter and the heavier olefin-containing hydrocarbon feed stocks and products.
The prior art further just used metal catalysts for disproportionating and isomerizing either singularly or in admixtures, but made no distinction between where these were located relative to the input of these feed stocks or which catalyst should be the first for reaction with the feed stock. The objective in the prior art was thus to make the deepest possible internal olefin of both light and heavy species before or during the disproportionation including symmetrical internal olefins. This was highly desirable when the goal was to create a mid-range olefin-containing hydrocarbon, but not for the production of heavier olefin-containing hydrocarbons from lighter olefin-containing hydrocarbons, where specifically a formation of asymmetrical olefins is desired.
It is the object of the invention of this process to create improved yields of heavier olefins using a substantially narrow range of lighter olefin-containing hydrocarbon feed stock in a reaction distillation column containing metal catalysts and controlled temperature and pressure for reacting the narrow range of lighter olefin-containing hydrocarbon feed stock to form the improved yields of the heavier olefins. In the process of reacting the lighter olefin-containing hydrocarbon feed stock to form the improved product yields of the heavier olefins, the removal of the lighter olefin-containing hydrocarbons and other light hydrocarbons occurs.
An object of the process of this invention is to create the improved yields of heavier olefins without using high temperatures and/or longer residence time in the systems of these processes, so as to limit the formation of unwanted by-products which are undesirable in the desired product and which may interfere with the formation of the desired heavier olefins or reduce the yields thereof.
Yet a further object of the process of this invention is to shift the equilibrium of the reaction toward the formation of heavier olefin-containing hydrocarbon feed stock by reacting the lighter olefin-containing hydrocarbon feed stock with the metal catalysts and then controlling the pressure and temperature to allow the lightest unwanted olefins and other light products produced by the reaction with the metal catalysts to go into vapor phase for its removal from the reaction distillation vessel overhead.
Also an object of this process invention is to allow even the lightest olefin-containing hydrocarbon feed stocks such as 1- and 2-butene and propylene to be reacted with metal catalysts in the controlled temperatures and pressures of this process for the creation of more valuable heavier olefin-containing hydrocarbon products such as C5 to C10, which have significantly greater monetary value than the products of 2-pentene and 3-hexene.
The object of the process of this invention further allows the creation of heavier olefins from a narrow range of lighter olefin-containing hydrocarbon feed stock and then running the narrow range of heavier olefins created through another step to create yet heavier olefins.
A yet further object of this process invention is to utilize the isomerization process to adjust the location of the olefinic double bond to a predominantly asymmetrical location in the olefin molecules and then disproportionate the olefin molecules, which effectively cuts them at the double bond and recombines the asymmetrical fragments with other olefin molecules which have been disproportionated to create heavier olefin molecules and light olefin molecules and then isomerized those heavier olefin molecules and then disproportionate them again. After all disproportionation in the process the lighter undesirable olefin-containing hydrocarbons are removed in the vapor phase leaving the heavier olefins to be isomerized again before the process continues in the steps to the desired heavier olefin product.
Also an object of this invention is the use of both isomerization and disproportionation catalysts with olefin-containing hydrocarbon feed stocks and reaction products in a vapor and liquid phase in relative low temperatures and pressures to achieve a desired range of heavier olefin end products.
Further it is an object of this invention to provide at least one vapor/liquid contacting zone to facilitate the separation of the lighter olefin-containing hydrocarbons and the collection of the heavier olefins either as desired products or for further reacting in the reactive distillation column.
It is also an object of this invention to adjust the type of catalysts and where that catalysts is located as the predetermined point for the first exposure to the lighter olefin-containing hydrocarbon feedstock depending on the degree of symmetry or lack of symmetry of the olefin bonds on the lighter olefin-containing hydrocarbon feedstock which are being fed into the reactive distillation column at that predetermined point in the reactive distillation column.
Yet further and additional benefits and improvements of the process of this invention will be appreciated by other skilled in the art and those advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description and diagrammatic drawings.